The quadricyclane, being an important high-energy aerospace fuel, has a density of up to 0.98 g.cm−3, and the ice point lower than −40° C., and can be used in propelling systems of aerospace vehicles, for example, such as rockets, guided missiles, satellites, and space crafts. As compared with kerosene fuels, the quadricyclane has the high-energy advantage, and as compared with hydrazine fuels, it has the advantage of the high safety.
The quadricyclane may be synthesized via a photochemical process, that is, norbornadiene, as the starting material, is used to form the quadricyclane via the intermolecular addition reaction of norbornadiene with ultraviolet radiations and in the presence of an organic photo-sensitizer or a solid photocatalyst as the catalyst for the reaction.
Current photo-catalytic isomerisation reaction of norbornadiene is conducted by utilizing high-voltage or medium-voltage mercury arc lamps, and however, because light radiations will produce large quantities of heat energies, a quartz cooling jacket which is transparent to ultraviolet lights is necessary so as to cool the reaction system. During the light induced isomerisation, some side reactions will be involved, and the main of them is that the reactants are polymerized under light induction to form some cokes which adhere on the outer surface of the quartz jacket so that the light transmission is hindered, thereby resulting in that the reaction become slow even is stopped. In addition, the quartz reactor is hardly to clean and is fragile and high cost.
In the U.S.A patent US2004/0054244A1, in order to inhibit coking side reactions during the reaction, amine inhibitors are added to the reactants, and a flowing circulation quarters reactor is designed. In the reactor, a 1300 W medium-voltage mercury arc lamp is employed; the reaction solution containing 0.4 wt % ethyl Michier's Ketone is allowed to flow through the reactor with the rate of 1.2 ml/min; and after the reaction is circulated for 25 hours, the conversion rate is close to 100%. In the process of the patent, the photo-sensitizer is directly left in the resultant quadricyclane without any purification.
In the German patent DE3625006A1, a rotary brush is designed. The reaction is conducted by utilizing photo-sensitizers, and during the reaction, the brush is periodically used to clean cokes on the wall of the quartz reactor.
Although the processes as described in the above patents inhibit coking in some extent, the following disadvantages are still involved: (1) reactors are made of quartz which is in high cost and fragile; (2) photo-sensitizers are remained in the product, and it can influence the purity of quadricyclane; (3) in views of the reaction mechanisms, it is impossible to completely inhibit the coking reaction, and thus after a long time reaction, there are always some cokes formed on the wall of the reactor; and (4) the reactions are in the intermittent manner which is disadvantageous to large-scale productions.
In order to overcome the above difficulties, the objective of the invention is to provide a novel process for producing quadricyclane wherein a continuous process for producing highly-pure quadricyclane can be achieved by integrating the reaction and the purification.
Individual reference sign in the above figures has the following meanings: 1. norbornadiene; 2. reaction-rectification integral reactor; 3. distiller; 4 highly pure quadricyclane; 5. stainless steel cylinder; 6. composite catalyst-filler layer; 7. quartz tube; 8. ultraviolet light source; 9. norbornadiene storage tank; 10. reactor; 11. rectification column; 12. cokes.